The treatment of effluents very rich in COD (Chemical Oxygen Demand) upstream the biologic purification units is quite challenging. For this reason, a few electrochemical techniques of COD pre-treatment have been explored. COD oxidation may be carried out by electrolysis on anodes characterised by high oxygen evolution overvoltage or with similar specific electrocatalytic properties.
The tin and antimony oxide-coated electrodes are included among those, and reference will be made in the following as a non-limiting example of high oxygen overvoltage anodes. Such electrodes have been used in plain electrolysers known in the art, for instance in perpendicular flow-type electrolysers. In such electrolysers the solution to be treated passes alternatively through anodes and cathodes consisting of meshes or sponges. The COD reduction of several effluents by this technique was actually observed, nevertheless a very low faradic yield is associated to such system, even though the COD reduction is as low as about 50%.